by Martha T. Moore, USAToday

by Martha T. Moore, USAToday

Kansas Republican Sen. Pat Roberts held on to win his party's nomination Tuesday against Tea Party-backed primary challenger Milton Wolf in a race that tested the ability of insurgent Republicans against establishment candidates. Instead, it was a Tea Party incumbent, Michigan Rep. Kerry Bentivolio, who lost the GOP nomination to a business-backed Republican candidate.

Bentivolio is only the third incumbent to lose renomination in the midterm elections, despite public opinion polls now showing that voters not only don't like Congress but don't even like their own representatives.

Roberts, who is running for a fourth term, ran into trouble with voters when it was reported that he no longer had a home in Kansas but rented a room from friends. Wolf, a radiologist and distant cousin of President Obama, tried to portray Roberts as out of touch with Kansas - but his own campaign stumbled when his Facebook postings of gunshot wound X-rays, with caustic commentary, came to light.

In a suburban Detroit district, Republican Dave Trott had help from Mitt Romney and his own checkbook - he put $2.4 million into his campaign - to beat first-termer Bentivolio. The former reindeer farmer unexpectedly found himself in office in 2012 when the incumbent was disqualified for fraudulent ballot petition signatures.

Longtime Texas Rep. Ralph Hall, 91, and Majority Leader Eric Cantor in Virginia, both Republicans, are the only other incumbents to lose their primaries this year.

Incumbents elsewhere in Tuesday's primaries won by comfortable margins. Kansas GOP Rep. Mike Pompeo held off a comeback bid by former eight-term congressman Todd Tiahrt, who ran in favor of bringing back earmarks, the discretionary Congressional spending that Tea Partiers oppose. Libertarian Justin Amash of Michigan also won his primary.

Kansas Rep. Tim Huelskamp, also elected in the 2010 Tea Party wave, voted repeatedly against a farm bill and also opposed renewable fuel standards despite his cornfield- and ethanol-heavy district, but he survived a challenge from farmer Alan LaPolice.

In Michigan's 12th District, Debbie Dingell, wife of retiring Rep. John Dingell, handily won the Democratic primary for the safe "blue" seat. Her election in November would make her the third Dingell to hold the seat: Her husband was first elected in 1956, succeeding his father, who had held the seat since 1933.

Democratic Rep. John Conyers, first elected in 1964, won his party's nomination by a wide margin over pastor Horace Sheffield, though he only made the ballot because a federal court ruled unconstitutional the requirements for ballot petitions that he had failed to meet.

Washington state voters will choose between two Republicans, Clint Dider and Dan Newhouse, to succeed retiring Rep. Richard "Doc" Hastings in a heavily Republican district. They were the top two finishers among a dozen candidates in a mail-in ballot primary.